DUNES AND DEPEESSIONS. 



265 



from the Bad Woods to a short distance beyond Pine 

 Creek, forty miles. 



2. Sand hills of the Souris. 



3. Sand hills and dunes of the Qu'appelle. 



4. Sand hills and dunes of the South Branch. 



5. Sand and gravel ridges north-west of the Touchwood 

 Hills. 



CIRCULAR DEPRESSIONS. 



This curious disposition of the drift, probably due to a 

 re-arrangement of its materials, is of not uncommon oc- 

 currence south-east of the Touchwood Hills. Circular 

 depressions varying from 100 yards to half a mile in 

 diameter, appear in the prairies, generally surrounded by 

 a ridge of sand or gravel. Many of them are quite dry, 

 others hold water, which is generally brackish. The 

 deepest and largest depression noticed was about 600 

 yards across and 40 feet below the general level. 



DENUDATION. 



An adequate conception of the effects of denudation 

 in the basin of Lake Winnipeg can be best attained if we 

 revert to the period when the Cretaceous shales now 

 forming the summit and flanks of the Turtle, Biding, 

 Duck, Porcupine, and Pasquia Mountains, occupied the 

 basins of Lakes Manitobah and Winnipeg, and found their 

 eastern limits near the present outcrop of the Laurentian 

 Series. In order to complete our view of the extent of 

 this great physical movement, we must conceive the same 

 shales and sandstones, (in part overlaid by Tertiaries fill- 

 ing the depressions or valleys in the Cretaceous rocks, 

 the result of previous denudation) forming an unbroken 

 table-land to the Grand Coteau de Missouri. These 

 relations become more evident upon an inspection of the 

 sections. 



